In this series, laryngeal preneoplastic lesions were evaluated by the classifications of the World Health Organization (WHOC), Ljubljana (LC) and squamous intraepithelial neoplasia (SINC) by multiple observers. The inter-observer agreement (IA) by WHOC for laryngeal lesions had been previously evaluated, but to the best of our knowledge, there are no data for LC and SINC. H&E stained slides from 42 laryngeal biopsies were evaluated by fourteen participants according to WHOC and LC, and SINC was additionally applied by 6. The results were analyzed statistically. The diagnoses which were favored by most participants for each case, according to WHOC, were as follows: squamous cell hyperplasia (n = 5; 12%), mild dysplasia (n = 11; 26.2%), moderate dysplasia (n = 12; 28.6%), severe dysplasia (n = 7; 16.7%), carcinoma in situ (n = 5; 12%), and invasive squamous cell carcinoma (n = 2; 4.8%). There was a significant difference between the participants for all three classifications; some participants gave lower or higher scores than the others. The mean correlation coefficients (MCC) of the participants were higher for WHOC compared to LC (0.55 ± 0.15 and 0.48 ± 0.14, respectively). The mean linear-weighted kappa (wKappa) values of participants were not significantly different (0.42 ± 0.10, 0.41 ± 0.12 and 0.37 ± 0.07 for WHOC, LC and SINC, respectively). The kappa values in this series are in agreement with those in previous literature for WHOC, and the similar results obtained for LC and SINC are novel findings. Although the MCC of WHOC was higher, as the wkappa was not significantly different, the findings in this series are not in favor of any of the classifications for better IA for pre-neoplastic laryngeal lesions. © 2010 Humana.